Internal combustion engines with power-to-weight ratios significantly higher than 1 Hp/lb which operate on low flash point fuels are enabling for powering Unmanned Aerial Vehicles (UAVs). Conventional Otto, Diesel and Wankel cycle engines even if constructed in advanced light-weight materials cannot meet the required power-to-weight and volume ratios and have high cost. A breakthrough in engine design, operational simplicity and ability to efficiently burn heavy fuels (JP-5, JP-8, DS2) has been demonstrated in a small 2 Hp engine exhibiting 1.1 Hp/lb which has been termed VS-engine. This patented VS-engine when constructed in advanced light-weight materials can be projected to produce power-to-weight ratios in the 1.5 – 2.5 Hp/lb, power-volume ratio approximately 7.5 Hp/in3, power density of 200 – 300 Hp/ft3, and produced at approximately ½ the cost of an Otto engine. In a joint program with Southwest Research Institute (SwRI), the VS-engine will be modeled utilizing advanced materials to define performance potential, and an engine will be produced in advanced materials and operated with heavy fuels to demonstrate exemplary performance.